Diving Medicine - Firefighting
Fire fighters involved in search and rescue operations
occasionally use SCUBA (Self-Contained Underwater Breathing Apparatus) and other
underwater breathing systems in the line of duty. Use of these systems in
the underwater environment may present a number of unique occupational exposures
with potential medical implications. A full understanding of these
exposures and their potential medical consequences will allow the diver to
train, plan, and work in a manner which minimizes the potential for work related
The following pages, although by no means a complete discussion of diving
medicine, will provide the following information:
1) A brief overview of the
history of diving.
2) An outline of
basic diving physics and effects of diving on the body.
3) A review of the major
medical complications of diving including:
•Pulmonary Over-Inflation Syndrome
4) A discussion of diving
fitness for duty criteria.
5) Discussion of
= training + planning.
•Diving Safety and Planning
•Diving Emergency Assistance
for answers to more complex diving medicine questions.
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Health and Safety Department.
1) A Brief
History of Diving Medicine - (excerpts from Bove's Diving Medicine, 3rd
Diving has been used as a means of underwater work and exploration for
thousands of years likely originating with the use of breath-hold diving in
pursuit of shells, pearls, and lost tools. Many commercial breath-hold
divers in the commercial pearl/shell industries regularly "free dive" to depths
of 60-80 feet, with world records held in excess of 400 feet.
Use of modern diving bells extended working time by trapping air in an
inverted container while workers operated inside. Diving bell activity is
reported as early as 332 BC, when Alexander the Great deployed military divers
from diving bells for enemy vessel destruction at the Siege of Tyre.
Later, the innovation of surface supplied diving allowed workers to operate
on the ocean floor free of constraint, first reported by August Siebe in 1819.
This technology evolved into the classic "deep-sea" diving suits used by the US
Navy including the Mark V diving suit, used by the Navy until 1982.
During the WWII era, two major diving advances occurred which dramatically
altered diving technology. The first, Jack Browne's triangular diving
mask, was widely used by divers engaged in commercial activities. The
second, the 1943 invention of self-contained underwater breathing apparatus
(SCUBA) and the demand regulator by Cousteau and Gagnon, caused the growth of
sport diving and allowed the use of diving in civilian applications.
Although a variety of underwater breathing systems are available in the
commercial marketplace, content of this site will focus primarily on open
circuit scuba systems, the breathing apparatus most likely to be used by fire
fighters and other public safety divers.
2) Basic Diving Physics
An understanding of dive medicine first requires an understanding of the
physics, barometric (pressure) changes, and gas effects caused by descent of the
diver in the water column.
At sea level, atmospheric pressure exerts approximately 760mm Hg (1 ATM or
14.7 psi) on the human body. During a diver's descent in the water column,
pressure increases linearly at a rate of an additional 760 mm Hg (1 ATM) for
every 33 feet of descent in sea water (34 feet in fresh water). A diver
descending to 99 feet would therefore be exposed to a total of 4 ATM [1 ATM +
(99ft/33)] or 4 times as much pressure as experienced on the surface.
Pressure and pressure gradients have a number of potential effects on the diver
including: barotrauma, pulmonary over-inflation/air-gas embolism secondary
to uncontrolled ascent, increased "on-gassing" of nitrogen creating the
potential for decompression sickness upon return to the surface, and nitrogen
narcosis caused by the "intoxicating" effect of elevated nitrogen levels at
The relationship between pressure and volume is best described by Boyle's Law
which states: given any constant temperature, pressure and volume are
inversely related according to the equation P1V1 = P2V2.
It is easiest to imagine this relationship as illustrated below.
If a garbage bag were filled with 1 liter of air and then taken from the
surface to 33 feet of depth, the air would occupy only half it's original volume
(The pressure has doubled). Similarly, a diver on SCUBA making an
uncontrolled ascent from 33 feet without exhaling, would double the volume
of air in his lungs, potentially causing pulmonary over-inflation and an air-gas
A second concept essential to understanding diving medicine is the
relationship between gas partial pressure and the ability of a gas to dissolve
in a solute. Henry's Law states that the amount of gas which will dissolve
in a liquid at any given temperature is a function of: 1) the partial
pressure of the gas in contact with the liquid, and 2) the solubility
coefficient of the gas in the liquid. As a diver descends in the water
column and pressure increases, blood nitrogen levels gradually rise as more
nitrogen is dissolved in the blood. These elevated nitrogen levels, at
depths greater than 100 feet, may cause an intoxicating effect known as nitrogen
narcosis. Although initially limited to dissolution in the bloodstream,
the nitrogen load is gradually absorbed by other body compartments. Upon
return to the surface, as pressure decreases, this nitrogen may come out of
"solution" and cause decompression sickness if the diver has exceeded
An example of this concept is a shaken carbonated beverage can. While
pressurized, the carbon dioxide remains in solution in the beverage.
However, if the can is opened and the is pressure removed, the carbon dioxide is
no longer soluble under the reduced pressure and comes out of solution.
Decompression sickness occurs in a similar manner only reducing the pressure
allows nitrogen instead of carbon dioxide to escape for the body.
Implications of Diving
Barotrauma refers to trauma or damage caused to body tissues by
the mechanical effects of a pressure differential (between a body cavity and the
hydrostatic pressure surrounding the body). For barotrauma to occur in a
body area, the following five conditions must be met.
i) There must be a gas filled space
ii) The space must have rigid walls
iii) The space must be enclosed
iv) The space must have vascular penetration
v) A change in ambient pressure must occur.
A diver descending in the water column must "equalize" to
prevent a middle ear squeeze from occurring as the outside pressure exceeds that
inside the middle ear. This scenario commonly occurs in the context of
eustachian tube dysfunction (due to anatomy or congestion) or secondary to
inadequate equalization during descent. If pressure continues to increase
without equalization, the ear drum will eventually burst as the pressure
Barotrauma is must frequently seen during descent in the water
column (referred to as a "squeeze"), but may also occur during ascent ("reverse
squeeze"). Middle ear squeeze is the most common form of barotrauma;
however, other types of barotrauma include: sinus, external ear, thoracic, face
mask, gastrointestinal, and tooth squeezes.
Prevention: Proper equalization during diving
prevents most sinus and ear squeeze from occurring. Given this fact,
diving should not be attempted if the diver is unable to clear secondary to
congestion. If decongestants are used, avoid those with a narcotic or
Treatment: To treat squeeze during descent: Stop
descent. If efforts to equalize fail, ascend a few feet, and avoid
clearing during ascent or forceful valsalva. If further efforts to
equalize pressure fail - abort the dive. If the diver reports dizziness,
abort the dive, and evaluate need to launch the stand-by diver. Follow-up
with personnel trained in diving medicine.
To treat a reverse squeeze during ascent: Stop ascent and
if clearing does not occur, descend 3 feet. Ascend slowly. Avoid
forceful valsalva. Evaluate need to launch stand-by diver. Follow-up with
personnel trained in diving medicine.
B) Pulmonary Overinflation Syndromes (POIS)
Pulmonary over-inflation syndromes are a group of disorders
caused by over expansion of the lung. These syndromes generally occur
secondary to ascent without exhaling. This group of disorders includes:
pneumothorax, mediastinal emphysema, subcutaneous emphysema, and air gas
Pulmonary overinflation is most commonly seen in the context of
inadvertant breatholding during an uncontrolled ascent by an inexperienced or
poorly trained diver. Following Boyles Law, the air volume of a diver who
has taken a breath at depth exceeds the divers lung capacity causing
overpressurization. As little as a 90 cm H2O overpressurization
may cause the alveoli in the lung to rupture, potentially allowing release of
air into body spaces including the mediastinum, the neck, the chest cavity, or
the pulmonary vasculature (discussed below).
Overinflation is most likely to occur near the surface as the
greatest pressure and volume changes occur in this zone. Constant
exhalation is therefore necessary any time a diver is surfacing, as failure to
exhale may result in overinflation and consequent alveolar rupture.
Pneumothorax - is caused by air outside the lung that is
trapped in the chest cavity
Mediastinal and Subcutaneous Emphysema - are caused by
air which is trapped behind the breast bone in the mediastinaum (mediastinal
emphysema), or air which has dissected into the neck (subcutaneous emphysema)
Air Gas Embolism - is caused by air which has entered the
pulmonary capillaries (lung blood vessels) and enters the left side of the
heart. After leaving the left ventricle, these air bubbles may either
travel to the coronary arteries (heart blood vessels), or the cerebral arteries
which may cause symptoms similar in many respects to a heart attack or stroke.
The diagram below illustrates this process.
Symptoms: Symptoms associated with pulmonary
overinflation syndromes range from shortness of breath seen with pneumothorax,
to changes in voice and substernal air trapping seen with mediastinal and
subcutaneous emphysema, to air gas embolism symptoms which may include mental
status changes and loss of consciousness.
Any time a diver losing consciousness within 10 minutes of
surfacing or upon surfacing, should be assumed to have an air gas embolism
until proven otherwise. Symptoms generally occur within minutes of an
uncontrolled ascent, and should be referred to a medical professional
Prevention: Prevention of pulmonary over-inflation
syndrome should first focus on a medical selection process eliminating those
with evidence of active lung disease or a history of spontaneous pneumothorax.
Those with respiratory disease including (but not limited to) asthma, lung
surgery, and traumatic pneumothorax should undergo a full medical examination
before diving. Second, training in diving physics/physiology and correct
use of diving equipment is essential. Third, An emergency contigency plan
should exist for treatment of diving injuries including: location and
contact numbers for the nearest recompression facility (contact DAN for
Treatment: Treatment of pulmonary overinflation
syndromes differs according to severity of symptoms, but whenever suspected
should be referred to a medical professional familiar with diving medicine.
Pneumothorax - a mild pneumothorax may be treated with
100% oxygen by face mask, however, more severe cases may require placement of a
chest tube, a procedure which should only be performed by experienced medical
personnel. A pneumothorax seen in combination with suspected air gas
embolism should not prevent emergent recompression.
Mediastinal and Subcutaneous Emphysema - minor
mediastinal or subcutaneous emphysema treatment may be accomplished through 100%
oxygen therapy; however, more severe cases may require recompression therapy.
The injured diver should be immediately transfered to an emergency room facility
for evaluation by a medical professional familiar with diving medicine.
Chest xrays should be taken to rule out pneumothorax.
Air Gas Embolism - divers suffering from air gas embolism
may require immediate basic life support/CPR upon surfacing so remember your
ABC's (Airway, Breathing, Circulation). Be sure the diver has a patent
airway (free of vomit, debris), check breathing and circulation, and begin CPR
if indicated. Alert the emergency transport team immediately and alert the
receiving medical/recompression center so recompression therapy may be utilized
as early as possible.
If 100% oxygen is available, it should be administered by face
mask. Oxygen should only be discontinued if convulsions consistent with
oxygen related seizure occur. Cover the diver with blankets and transport
the patient to the nearest emergency room in preparation for transfer to the
nearest recompression chamber. In route monitor for and treat cardiac
dysrhythmias per ACLS protocals. Hydration is recommended when possible.
C) Decompression Sickness
Decompression sickness or "the bends" was first reported by Sir Robert Boyle
in 1670 during animal pressure experimentation when Boyle reported, "... a viper
furiously tortured in our exhausted receiver...that had manifestly a conspicuous
bubble moving to and fro in the waterish humour of one of his eyes." The
pressure related disease acquired it's nickname "the bends" after workers
emerging from pressurized construction on the Brooklyn Bridge adopted a posture
similar to fashionable ladies of the period ("the Grecian Bend" - below) because
of symptoms of decompression sickness.
As a diver descends in the water column, the combination of increased
pressure (Boyles Law) and consequent increased solubility of nitrogen in the
body's tissues (Henry's Law) causes an increase in the "on-gassing" of nitrogen.
Air is made up of approximately 79% nitrogen, which on the surface, is easily
cleared from the body. However, as the diver goes deeper, the pressure
increases, increasing the partial pressure of nitrogen, and the "on-gassing" of
nitrogen exceeds the body's ability to clear the gas. The deeper the diver goes,
the faster this process occurs. A diver with a "nitrogen burden", upon
surfacing may allow nitrogen inside the body to come out of saturation (similar
to removing the lid from a shaken/pressurized cola can) causing bubble
formation. These bubbles may cause joint pain, sensory changes, limb weakness,
and in severe cases paralysis and death, the symptoms being dependent upon
location of bubble formation (joints, spinal nerves, spinal cord, etc.). This
process is known as decompression sickness, or "the bends". Onset of these
symptoms generally occurs within 12 hours of surfacing from a dive (90% within 6
hours), however, a physician familiar with diving should be consulted anytime
decompression sickness is a potential diagnosis.
History: Nitrogen burden and onset of symptoms within 12 hours of
surfacing (90% within 6 hours)
|DCS Type 1
Pain - Periarticular (joint)
Mottling of the skin (cutis marmarota) - shown below
| DCS Type 2
Pulmonary - cough, "chokes"
Spinal - sensory change, weakness
Inner ear - ringing, hearing change
Cerebral - mental status changes
Prevention: Decompression sickness may be prevented by following these
basic steps: 1) Plan the dive prior to entering the water and stick to it. 2)
Strictly adhere to no-decompression (No-D) limits as listed in available
commercial dive tables. 3) Dive team members should be held to physical fitness
standards. Adipose tissue (fat) readily absorbs nitrogen, increasing the
potential for decompression sickness. 4) Train for diving often. When
adverse conditions do occur, as is common in diving, the diver and the diving
supervisor must know how to deal with the situation. 5) An emergency
contigency plan should exist for treatment of diving injuries including:
location and contact numbers for the nearest recompression facility (contact DAN
for recognized chambers). 100% oxygen for treatment until recompression.
Treatment: Immediate transfer to a recompression chamber for
evaluation by a physician familiar with diving medicine. In route, oral or
iv hydration is recommended. If available, 100% oxygen should be
administered by face mask.
D) Nitrogen Narcosis
As mentioned above, increases in pressure will increase body nitrogen
saturation causing a progressive "intoxicating" nitrogen effect generally seen
in divers at depths in excess of 100 feet. This effect is highly variable
between individuals, but many divers refer to "the martini rule" which suggests
that every 50 feet of sea water descended in excess of 100 feet has the effect
of drinking a martini on an empty stomach. Most divers report symptoms similar
to alcohol intoxication including decreased reasoning ability, increased
reaction times, lightheadedness, and euphoria. Disorientation and poor judgement
may result, placing the diver at risk in the unforgiving underwater environment.
Nitrogen narcosis generally resolves with ascent from depth and
acclimatization may occur in divers with a history of exposure. Alternative
breathing mixtures should be considered if nitrogen narcosis is regularly
reported as symptoms may effect diving safety.
4) Fitness for diving duty
The underwater environment presents a number of unique stressors which
require that divers maintain a reasonable level of physical/physiological
psychological fitness while acting as public safety divers.
Difficulties encountered in the underwater environment include:
-Heat loss due to exposure to water likely to be below the core body
-Physical demands of propulsion in the underwater environment
(cardiovascular, pulmonary, etc.)
-Respiratory demands of breathed compressed gas, etc.
These and other physiologic demands of diving require the diver to maintain a
sound level of fitness and be comfortable underwater as lack of fitness, and
lack of diving proficiency may both have severe consequences in the unforgiving
A listing of fitness for duty suggestions may be found at the attached link,
Medicine Online. Those with questions specific to cardiovascular
disease might also try
Bove's Scubamed.com. Although these sites give excellent fitness for
duty outlines, medical conditions vary by individual and should be reviewed by a
medical professional familiar with diving medicine before beginning a diving
regimen. Personnel involved in diving should also discuss their job
responsibilities with their primary care physician during their annual physical
5) Diving Safety =
Planning + Training
The US military has for years performed diving operations in hazardous
environments while maintaining a solid safety record, minimizing risk to divers.
These safety records are the result of planning, training, and exhaustive
preparation before each dive. Similar to military diving, fire fighters
involved in search and rescue operations are required to operate in less than
optimal diving conditions and may be forced to make difficult decisions in an
environment which, like firefighting, is inherently unforgiving.
A critical element of any diving operation is an emergency planning checklist
which should include use of a diving safety and planning checklist and an
emergency assistance checklist. Both these may be found below.
Diving Safety and Planning
STEPS IN PLANNING OF DIVING OPERATIONS
Detailed advanced planning is the foundation of
A) ANALYZE THE MISSION FOR SAFETY
the mission objective is clearly defined
Determine that non-diving means of mission accomplishment have been
considered and eliminated as appropriate
Coordinate emergency assistance
relevant operational instructions
B) IDENTIFY AND ANALYZE POTENTIAL HAZARDS
__ Exposure of personnel to extreme conditions
__ Adverse exposure of equipment and supplies to elements
__ Delays or disruption caused by weather
__ Sea sickness
__ Water entry and exit
__ Handling of heavy equipment in rough seas
__ Maintaining location in tides and currents
__ Ice, flotsam, kelp, and petroleum in the water
__ Delays or disruption caused by sea state
3. Underwater and Bottom:
__ Depth which exceeds diving limits or available equipment
__ Exposure to col temperature
__ Dangerous marine life
__ Tides and currents
__ Limited visibility
__ On-site Hazards:
__ Local marine traffic and other operations
__ High powered active sonar
__ Radiation contamination and other pollution (chemical,
sewer outfalls, etc.)
__ Mission hazards:
__ Decompression sickness
__ Communication problems
__ Other trauma
__ Objective hazards:
__ Shifting or working of object
C. SELECT EQUIPMENT,
PERSONNEL AND EMERGENCY PROCEDURES
__ Diving Personnel:
__ 1. Assign a complete and properly qualified Diving Team
__ 2. Assign the right man to the job
__ 3. Verify that each member of the diving team is properly
trained and qualified for the equipment and depths involved.
__ 4. Determine that each man is physically fit to dive,
paying attention to:
__general condition and any evidence of fatigue
__record of last medical exam
__ear and sinuses
__severe cold or flu
__use of stimulants or intoxicants
__ 5. Observe divers for emotional readiness to dive:
__motivation and professional attitude
__stability (no noticeably unusual or erratic behavior)
__ 1. Verify that diving gear chosen and diving techniques are
adequate and authorized for mission and particular task.
__ 2. Verify that equipment and diving technique are
appropriate for the depth involved
__ 3. Verify that life support equipment has been tested and
__ 4. Determine that all necessary support equipment and tools
are readily available and are appropriate for the mission.
__ 5. Determine that all related support equipment including
winches, boats, cranes, floats, etc. are operable, safe, and
controlled by professionals.
__ 6. Check that all diving equipment has been properly
maintained (with appropriate records) and is in full operating condition.
Provide for Emergency Equipment:
__ 1. Obtain suitable communications equipment with sufficient
capability to reach outside help; check all systems for proper operation.
__ 2. Verify that a recompression chamber is ready for use and
available within the required timeframe. Have emergency numbers on-hand.
__ 3. Verify that a stocked first aid kit is available
__ 4. If oxygen is being used for stand-by first aid, be sure
the tank is full, properly pressurized, and that masks, valves, and
accessories are fully accessible.
__ 5. If a resuscitator will be used, check apparatus for
__ 6. Verify that emergency transportation is either standing
by or on immediate call.
Establish Emergency Procedures:
__ 1. Know how to obtain medical assistance immediately
__ 2. For each potential emergency situation, assign specific
tasks to the diving team and support personnel.
__ 3. Complete and post the Emergency Aassistance Checklist;
ensure that all personnel are familiar with it.
__ 4. Verify that up-to-date copies of decompression tables
__ 5. Ensure that all divers, boat crews, and other support
personnel understand diver hand and line pull signals.
__ 6. Predetermine distress signals and call-signs.
__ 7. Ensure that divers have removed anything from their
mouths which could cause choking during the dive (gum, dentures, tobacco).
__ 8. Thoroughly drill all personnel on emergency procedures
giving attention to cross-training. Drills should include:
Emergency recompression, fire, rapid dressing.
restoration of breathing, eletric shock, entrapment, rapid undressing, first
aid, embolism, near-drowning, uncontrolled ascent (blow-up), lost diver.
D. ESTABLISH SAFE
DIVING OPERATIONAL PROCEDURES
Complete Planning, Organization, and Coordination Activities:
__ 1. Ensure contingency planning has been conducted.
__ 2. Develop a flexible operational plan (Dive Plan) and
state goals and tasks of each mission.
__ 3. Completely brief dive team and support personnel as
__ 4. Designate a qualified diving supervisor to be in charge
of the mission.
__ 5. Designate a recorder/timekeeper and verify that he/she
understands these duties
__ 6. Determine exact depth at the job site using a
pneumfathometer or commercial depth sounder.
__ 7. Verify existence of adequate compressed air for all
planned operations, plus an adequate reserve for emergencies.
__ 8. Ensure that no operations take place without the direct
knowledge of the diving supervisor.
__ 9. All efforts should be made to minimize bottom time.
Water depth and diver condition should govern bottom time (not the amount of
work needing done).
__ 10. Ensure that when using SCUBA systems, a boat can be
quickly cast off and moved to a diver in distress.
Perform Diving Safety Procedures, Establish Safety Measures:
__ 1. Ensure each diver checks his/her own equipment in
addition to checks made by tenders, technicians, and other support personnel.
__ 2. Designate a stand by diver for all diving
operations; the standby diver shall be dressed to the necessary level and be
ready to enter the water if needed.
__ 3. Assign buddy divers, when necessary, for all SCUBA
__ 4. Take precautions to prevent divers from being fouled on
the bottom. If work is conducted inside a wreck or other structure, assign
a team of divers to accomplish the task. One diver enters the wreck, the other
tends his lines from the point of entry.
__ 5. When using explosives, take measures to ensure that no
charge will be fired while divers are in the water.
__ 6. Brief all divers and support personnel on planned
decompression schedules for each diver.
__ 7. Verify that diving craft display proper signals, flags,
and lights for diving operations in progress.
__ 8. Ensure that protection against harmful marine life has
__ 9. Verify that proper safety and operational equipment is
aboard small diving boats/craft.
Proper Parties That Diving Operations Are Ready to Commence including: the
diving supervisor, ships bridge to ensure use of
mechanical devices/propellers/thrusters/sonar/mooring systems does not occur,
harbor master, coast guard (as required), recompression facilities, emergency
Diving Emergency Assistance
Diver's Alert Network (DAN) - (919) 684-8111
6) Related Links for Diving Medicine
Rodale's Scuba Diving
Undersea and Hyperbaric
Medical Society (UHMS)